1999 V70 Brakes? ABS? ???

[Luxobarge]

Originally Posted by SteveSarre

If the problem was an ABS wheel sensor, I don't see how it would trigger an engine light.

The ECU requires a vehicle speed signal, which I believe is obtained from the ABS controller. The vehicle speed is normally ( I believe) taken from the front nearside ABS sensor. If the vehicle speed signal is missing, then I'd imagine that a fault code might be generated, along with the Engine Management Light (EML).

I'm not totally sure whether the engine ECU or the gearbox ECU need the speed signal, or both, but I'm sure at least one of them does, and will generate a code/light if it's missing.

I do stand to be corrected on all of the above, but there's some logic there that would explain an EML with faulty or missing ABS unit.

[currymunster]

Hi everyone,
Well, I soldered all the connector joints and the power joints and refitted without the lid to see what happens.
The abs still works every time you brake, and I can still hear a ticking coming from the module/pump.
This ticking however changes speed with the vehicles speed and not the engine speed?
The weird bit though is that the abs light comes on and the symptoms stop and it drives normal again,,, only with the abs light on which will fail the mot in two weeks time.

I cleared the faults which were
P0500 (speed sensor)
P0600 (communication error)
I put the latter down to the abs module being missing and unable to communicate.
Any ideas anyone?
Oh, and the speedo works fine?

[SteveSarre]

Hu Currymunster,


I don't understand "the symptoms stop and it drives normal again".
So is the ticking intermittent?

What happens if you unplug the power to the ABS module, and drive it?

Steve

[currymunster]

Originally Posted by SteveSarre

Hu Currymunster,


I don't understand "the symptoms stop and it drives normal again".
So is the ticking intermittent?

What happens if you unplug the power to the ABS module, and drive it?

Steve

Hi,
It's not intermittent.
If I remove the fuse or module it drives fine but with no abs.
If I put everything back then clear the codes the symptoms are there.
Then the abs light comes on and the symptoms dissappear?

[volvo again]

It may be a faulty abs control module itself, even after resoldering the joints there could be an internal fault.
Might have to replace the complete module

[pff]

I had a very similar situation as did mike19691969 you can read about in this thread:
https://www.volvoforums.org.uk/showthread.php?t=286565

Sounds like your abs module is getting an incorrect speed at one wheel causing the abs to kick in, then no speed signal at all so the abs module goes into error mode at which point it turns itself off and stops mucking around with your brakes.
The abs module will reset itself and try again every time you start the car, it does a self test the first time you drive above a certain speed (15mph? somebody correct me) and then will decide if there is a problem or not.

The situation was that the wheel speed sensor was only very slightly too far away from the reluctance ring so that the speed signal for one side was, at first, misreading the speed (especially while turning or breaking) which causes the abs module to activate as it believes the car is skidding.
In my case the problem got very slowly worse and worse, the abs would 'kick in' whenever the brakes were used.
eventually i believe the speed sensor migrated far away enough from the reluctance ring to give no signal at all, at which point the abs module finally was able to work out there was a problem and take itself out of the loop and throw an error code.

I replaced both reluctance rings and the abs module and pump but the only problem was that rust on the knuckle had pushed the wheel speed sensor too far away from the reluctance ring.
the fix was as simple as sanding the rust off so the sensor could sit perhaps 1 or 2 millimeters closer to the reluctance ring, very difficult to see the problem by inspection.

What was very helpful was using VIDA/DICE which can live read the speed measured by each wheel sensor so you can narrow down the problem immediately to one corner. If there isn't anyone can lend you one (you are welcome to mine on the weekend if you want to drive 500 miles to it!) you can find them on ebay etc there are a few threads about it, i think a member on volvospeed offers a virtual machine image ready to go with VIDA installed which is apparently a difficult thing to do.

[SwedishBus]

If you can find a friendly Automotive Electrician near you, they would be able to oscilloscope the actual speed signal from the individual sensors and prove what pff is saying here. From your symptoms, he sounds like he is bang on the money; you have an eccentricity in the sensor/reluctor air gap (assuming you have no micro-cracking of the reluctor from rust pressure) which is leading the speed signal being misinterpreted.

A visual check would be slower, but come to the same conclusion in the end, however you would disturb the system you are trying to diagnose in the process of measuring - so you might lose the evidence as to whether you have fixed this or not!

[currymunster]

Thanks every one, for holiday coming up so am very busy at the moment. I have ordered a module and pump of flea Bay now.
I will fit the module and see. If no joy I'll remove the sensors and clean then all up.
No one round here with soft where or even a friendly auto electrician that I know of.
I'll keep you all posted on her until conclusion.
Thanks everyone

[mike19691969]

Have you sorted the missing bolt on the wheel sensor? I will be very surprised if this is more complicated than a false reading from a wheel sensor.

You are going the expensive route of throwing parts at the car in the hope that it fixes a problem that you are unsure of the origin.

You really need a read on VIDA, try posting on the " VIDA DICE owners UK" Facebook page, there is bound to be someone near you willing to help.

[Clan]

Originally Posted by currymunster

Hi - I Believe it is the abs module.
Seems to be lots of part numbers for it
Does any one know if they are interchangerble or does it have to be the exact part number?

You have already been advised that it is most likely the driveshaft moving away from the sensor due to not being secured with a bolt .. This is 90% the cause ...

The ABS modules started being coded about 2001 ...